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Why Skepticism About Computer Models Is Not A Good Reason For Skepticism About Climate Change

A week ago I made the case that human-caused climate change should stop being a political football and that both parties should simply accept it as a reality. One pretty pervasive argument against global warming that I didn’t address in that article was this one: that the belief in global warming is based on computer models that are inherently unreliable. I sent two of the most trenchant comments from that piece, from reader gwkimball and my Forbes colleague Daniel Fisher, to Donald Wuebbles, the Harry E. Preble Professor of Atmospheric Science at the University of Illinois, who I interviewed for the article. Below is an edited version of the question and of his response.

Update: The short version of this: all sciences use models; you don’t need the models to prove that climate change is true.

All human-caused warming claims – ALL – depend on the computer climate models to back out the ‘human’ component originating in carbon dioxide. We just learned in the financial crisis, relying too much on mathematical models to predict the behavior of complex systems can be dangerous. Everybody knows it has been getting warmer since the ice age. How can the scientists convince skeptics a) there has been a non-random acceleration in the past 150 years and b) it is due to burning fossil fuels?

Wuebbles responds:“The basis for human activities being the primary driver of the recent changes in climate is observation and the physical understanding of the processes that drive our climate system. Models of these physical processes further add to this understanding, especially for the future projections of further changes, but the basic science is based on observation.

“It should be noted that people do depend on models throughout their lives. Airplanes are designed using models, flown using models, and the weather analyses they use are based on the models that are very much akin to our climate models. The models we use in study of the Earth’s climate system are basically the integrators of our knowledge of how the atmosphere and Earth’s climate work, and they do quite a good job of explaining it.

“We depend heavily on observations in our analyses. The well-measured CO2 increase exactly fits with our understanding of the carbon cycle as being associated with the burning of fossil fuels and land use change. There is NO other explanation for the increase in CO2. You can’t just say it is natural cycles when the ice core observations show that CO2 levels haven’t been as high as they are now (or even close to as high as they are now) for over 800,000 years.

“Going further, we have observation-based analyses of the past 2000 years that tell us the changes in climate we have seen in the last 50 years are way outside the norm. Plus they fit with our basic understanding of the greenhouse effect that go back nearly two centuries. There are no natural cycles that can explain all of the observed changes we are seeing on Earth — the atmospheric is warming, the oceans are warming, the land is warming, and the ice is melting. Climate does not change randomly, it changes beyond the normal natural variability due to external forcings. In the past, nature played the major role in those through changes in the solar flux or through large volcanic eruptions. But nature cannot explain what we have seen the last 50 years (the Sun has actually decreased in flux slightly over that time). But the greenhouse effect and the increasing greenhouse gases do fit.

“What we are experiencing is outside of anything humans have seen on our planet and the only explanation that makes any real sense is that it is due to human actions.”

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About a year or so ago, I read an article online, authored by a prominent British climatologist. His take on the skeptics of global warming was this: Global warming is a fact and it is coming to your doorstep, regardless of how skeptical you may be of the science. It’s the 900 lb. gorilla in the room that a lot of skeptics choose not to acknowledge. Everything is getting warmer and the polar ice packs on both poles are melting. This is neither random nor cyclical – it’s man-made. As a species, we have begun to change the environment we live in on a global, climatological level. This isn’t like wiping out a species here or there, this is much, much bigger than that. More people living on less land due to rising oceans. Hmmm, think of the socio-economic and geo-political consequences of that.

Everything you wrote is certainly true. However, what you, and every other commenter did not respond to was Mr. Herper’s main point of this blog:” the belief in global warming is based on computer models that are inherently unreliable.”

What is not commonly realized is that all sciences use models, not just climatologists. Many sciences use models, especially those that cannot have laboratory experiments. Geologist use models [1], biochemists use models [2], cosmologists use models [3], this is simply how science is done for many sciences. There is nothing special or unique about climatologist using models.

Yes, CO2 levels are higher; no, CO2 level does not drive the natural variations of weather/climate nor does it explain the recent 17-year hiatus of global temperature change.

Yes, global temperatures have risen about 1° since the 1880s; no, selecting a low point in naturally varying temperatures and plotting a straight trend from the low point is not a valid metric anymore than selecting a high point in that variation … 1920s – 1930s … and plotting a straight trend indicates global cooling or no warming.

The fact is that the science is so unsettled and the “experts” so disingenuous that a decade ago claims were made to the effect that snow in Britain would be so rare that our children and grandchildren would not experience it. Now the story is that record snowfalls are “consistent with” … along with more rain/drought, cold/heat, fire, wind, pestilence, and plague … global warming aka climate change.

The fact is that increasingly, more scientists are now having second thoughts about their understanding of climate, or lack thereof.

Does climate change? Most certainly. Does human activity affect climate? Most certainly. Does CO2 have any impact on climate? A modest amount. Does human activity drive the variation in CO2? A modest amount.

The most significant human activity affecting recorded temperature during the past century is the locating of weather recording stations in parking lots, roof tops, and within encroaching urban heat zones.

There actually simple ways to demonstrate the information of what the climate is by the temperature record. This shows the natural variation itself is on a warming trend. La Nina is the cooler part of the natural variation and it is warming as well as the El Ninos. The trend is there.

I can think of no better sign that modern science is infected by the tendency to create models and predictions designed primarily to fulfill their own subliminal desires.

El Niños appear as if to be a thing of the past. NASA scientists contributed to a long running prediction of one this past year, with one predicted each month for over 6 months for with up to 66% certainty. Result: No Niño. Forecast is now ENSO-neutral through the next one to three seasons. See http://www.bom.gov.au/climate/enso/ for unbiased reporting of ocean oscillations.

As someone who models the behavior of proteins and drugs in the pharmaceutical industry I am well aware of the limitations of models in predicting the behavior of complex systems. I have little doubt that the planet has warmed and that human beings are responsible for it, but my main problem is with prediction. In my field we have scores of models that are extremely good at explanation but which fail at prediction because some tiny parameter has been left out. In addition these models are especially bad at predicting sudden changes or tipping points. Let’s remember that we are trying to predict temperature changes as small as 0.6 degrees which to me, given the sheer number of variables that have to calculated, seems pretty much impossible with current technology.

I also have to say that I don’t quite agree with the comparison of climate models with airplane models. In 1995 the Boeing 777 was designed entirely on a computer. But impressive as that is, the complexity of an airplane is much less compared to the complexity of a massive, heterogeneous entity like the climate that keeps on changing because of interaction with the biosphere. The right analogy might be to compare climate with an airplane that keeps on changing its size, shape and weight and has to interact in turn with a constantly changing medium that exhibits far more turbulence than what we are accustomed to. Needless to say, such an airplane would be far harder to model on a computer. In fact it’s worthwhile comparing airplane and climate models to airplane and drug models; in spite of much progress, we are very far from being able to design a drug on a computer, partly because for similar reasons it’s very hard to condense so many parameters into a single number (in this case the energy of protein-drug binding).

I am not saying climate models are not useful. I am asking whether they are reliable enough to dictate the earmarking of trillions of dollars for specific policy proposals that would affect the lives of millions.

Had we been able to predict the drought of 2012 effectively out several months, farmers could save billions of dollars. Increasing our skills through modeling would have its payback easily. Unfortunately it appears that instead we will cut back on our modeling budget. decreasing our uncertainty about the climate will easily have its payback.

Ashutosh Jogalekar here are two blog articles from someone who is a climate scientists actively evaluating climate models and it should help you better understand the recent divergence between the CMIP5 ensemble models and the HadCRUT4 temperature values.